The invention relates to the conditioning and feeding of textile fibers to an associated textile processing machine, and particularly to the pneumatic working of textile fibers inside a batt forming machine and the like.
In the past, many devices have been proposed for handling textile fibers in the processes of opening, cleaning, and feeding the fibers.
Fiber is delivered to textile mills in the form of highly compressed and densely packed bales. Within such hard bales the individual fibers are tightly matted, entangled and generally knotted together. Before these fibers can be made into an acceptable textile product, they must be progressively loosened, step-by-step, and ultimately separated to a fiber-to-fiber state. Such separation of the fibers is commonly called "opening" the fibers.
Great care must be exercised in the manner by which the fibers are opened or, otherwise, they can be curled, bruised, broken, or drawn into very tight tiny knots called "neps". Fibers in any of these conditions seriously degrade the quality of the textile product which can be formed. The requirement that the individual fibers must not be degraded during their processing, has posed serious limitations on the techniques available to textile machine designers as to how they can process the fibers from the hard bales down to the individual fiber-to-fiber state.
The well known textile carding machine is often used as the last process to provide the individual fiber-to-fiber separation which is required. The product taken from the doffer cylinder of a carding machine is a very fine web of fibers, which has the visual appearance that one might see if several spider webs were laminated atop each other--hence the name, "carded web". A carded web is extremely delicate and easily damaged because the only forces holding the web together is the natural curliness or crimp of the individual fiber ends which are loosely hooking on to one another. A carded web is not nearly as strong as a spider's web, because the latter has a chemical bonding at every point where the strands cross. For this reason, how one handles a carded web is extremely critical.
The Textile Industry can be broken down into two major groups the non-woven segment and the yarn making segment. In the non-woven segment, the webs of several carding machines are often laminated and the individual fibers bonded together to form the final product. Such bonding may be accomplished by either chemical means (such as latex binders, thermal fusion, etc.), or by physical interlocking of the fibers (such as by needle punching, etc.). To the non-wovens industry, both the cross-direction weight per unit area and the running-direction weight per unit area of the webs delivered by carding machines are extremely critical because such weights govern the quality of their end-product. Furthermore, since web spreading devices are often used immediately downstream of a line of carding machines, to spread the laminated webs even wider, web weight inconsistencies can adversely affect the effectiveness of such spreading devices and the subsequent processing steps.
The yarn making segment of the industry usually gathers the carded web into rope-like form which is called a "sliver". The sliver is generally drawn and spun into a yarn which is formed into a fabric by either knitting or weaving of the yarns. Because the ultimate quality of such fabrics is governed by the uniformity along the lengths of the strands of the yarns used, yarn makers have usually been more concerned with the running-direction weight uniformity of the carded web than they have been with the cross-directional web weight profile. Clearly, to universally meet the particular requirements of both segments of the textile industry, the webs produced by a carding machine need to have good and controlled weight properties in both the running-direction and the cross-direction.
For a given degree of carding quality, there are two principal factors which presently restrict the maximum production rate obtainable from conventional carding machines. First, how well the tiny fiber bundles have been loosened and separated before they are presented to the card's main cylinder. Second, the cross-direction density profile of the very thin sheet of fibers presented to the card's main cylinder. To compensate for the inadequate degree of fiber opening delivered from present day card feeding systems, "high performance" carding machines today often employ either one or two additional licker-in cylinders in series with the single licker-in cylinder which has been traditionally used on conventional carding machines. For reasons discussed below, such additional licker-ins do not provide the results expected or needed. Consequently, such carding machines cannot run at the full production rate potential which can be achieved.
The cross-directional density profile of the sheet of fibers presented to a card's main cylinder is important to high production carding for several reasons. First, if the cross-direction density profile has a uniform state, such as shown by FIG. 5, then the main carding cylinder carries a uniform fiber load across its full width and can run at the optimum or maximum production rate. Unfortunately, the cross-direction density profile of the batt delivered by present day card feeding devices look more like that illustrated by FIG. 4. Consequently, the carding potential across the card's main cylinder is not fully utilized and the production rate is thereby limited. Secondly, the surfaces of licker-in cylinders and main carding cylinders are covered with literally thousands of tiny teeth and both cylinders are run at very high surface speeds. Consequently, windage currents are created where the licker-in cylinder engages with the main carding cylinder to transfer the fibers carried in the teeth of the former cylinder. Such windage currents tend to blow the fibers toward the outside edges of the card at both the point of fiber transfer, and around the "working path" followed by the main cylinder. This results in a condition known as "light selvages", or carded webs which are substantially lighter on their edges than near their center region. At increased production speeds, increased windage currents are also created by the thousands of teeth carried on the surface of the doffing cylinder, which causes the delicate carded web to be blown about more violently after it is taken from the doffer, which causes web breaks.
To eliminate broken webs, modern "high performance" cards are equipped with complicated web gathering devices (such as belts or a plurality of turning wheels) which gathers the web into a sliver before the delicate web can be exposed to the effects of the doffer windage. However, such web shielding mechanisms are not without their own particular set of problems because they tend to accumulate a build-up of waxes or fiber spin finishes which picks at and snags portions of the tender web, which causes "end breaks" due to wrap-ups. Because they do not utilize a sliver, non-woven applications must use the full width web delivered by the card and, thus, cannot be fitted with such web shielding or gathering devices. Consequently, their current maximum rate of production has been limited by these factors. Therefore, the optimum solution for both non-woven and yarn making manufacturers is to provide a simple means to eliminate "light selvages" and, thereby, obviate the need for the problematical web shielding mechanisms which have heretofore been required to operate carding machines at increased production rates.
As mentioned above, the batts produced by present day card feeding devices have non-optimum cross-directional density profiles, such as shown by FIG. 4. This disadvantage comes about because the friction of the side walls of such card feeding devices dissipates a portion of the energy used to form the batts within their batt forming chambers--irrespective of how the packing work is done, whether by static pressure compaction of the tufts, or by vibrating plate compaction of the tufts, or the combination of both methods. Since sidewall friction cannot be eliminated, the solution is to form batts of fibers in such a way that the effects of sidewall friction are negated.
Another problem faced by modern textile mills is their need to exploit the profits available by operating with reduced inventories. New operational concepts, sometimes referred to as "just-in-time" and "quick response", permits such profits . However, to practice these operational concepts textile mills must have total flexibility as to how they supply fiber to each card in the mill. Then, each card can be quickly changed from one blend or mix to another, in order to match instantaneous production needs. Present day card feeding systems can offer such flexibility only at great capital cost and complexity in the distribution systems which are available.
It is known in the art that resting air may be drawn in from the room environment and accelerated by a fan to form a conveying airstream--which is passed through a fiber opening machine which is generating large tufts and flinging them into such airstream for transport to a downstream batt forming apparatus--which contains a fiber condensing screen to retain such tufts while exhausting the transport air back into the environment. Such art may be seen, for example, by reference to U.S. Pat. Nos. 4,769,873; 4,689,857; 4,462,140; 4,009,803; 3,851,924; 3,851,925; and 4,682,388.
With such devices, the air is used just once to convey fiber and all the energy contained in every pound of transport air, as it is dumped back into the environment, is consequently wasted. Additionally, before such air (large quantities are needed) is suitable to be returned to the room--where humans breath it--it must be properly filtered. It is well known that the frictional losses associated with passing large quantities of air through dense/efficient filter media, and the resulting economic costs, are enormous.
Furthermore, in order to make a first class endproduct, it is widely accepted that the weight variation of every square yard of carded web delivered by a carding machine must not vary more than plus or minus three to five grains from the nominal or mean operating value. As a frame of reference, such a tight weight tolerance is about equal to the weight of three U.S. Postage Stamps, each measuring about 7/8 inch.times.1 inch. It is very difficult to even measure such standards in a normal operating environment, because vibrating floors, the air currents from the room air conditioning system, and even persons breathing near the sensitive scales needed, all affect their weighing accuracy. Since the carded webs from "high performance" cards are spewing forth at the rate of about 2 to 6 linear yards per second, it is obvious that a crude simplistic approach--like, just opening some fibers and blowing them into box--is incapable of meeting modern production standards. To properly address the problems of producing a very high quality carded web, having the desired weight profiles, and doing so with the minimum expenditure of energy, requires considerable attention to every detail of the various processing steps involved along the way.
For the above mentioned reasons, and others which will become apparent below, such art as cited above is unsuitable to meet the objects of the present invention.
It is known in the art (for example, U.S. Pat. No. 4,520,531) that the cross-directional density profile of a batt delivered by a batt former may be altered through the use of a plurality of damper plates, positioned outside of a fiber condensing screen, to vary the amount of air flowing through different portions of the screen and, thereby, guide tufts to the general regions desired. Such art also teaches that a plurality of wedge shaped members may be actuated within an airstream to modulate the airflow passing through various portions of a fiber condensing screen, and/or that a plurality of blocking members may be moved in or out to vary the cross-sectional airflow area in order to direct various portions of the airflow through different zones of such fiber condensing screen. All of the above mentioned movable members, to alter the airflow through various regions of the fiber condensing screen, are operated in response to a plurality of sensors, disposed downstream of the batt forming apparatus, which feeds back control signals to a plurality of actuator means. The theory behind such devices is quite simple, where the air goes, tufts will later go. The art usually over-simplifies the theory and forgets several key scientific facts. First, tufts flung from the tips of the pins, on fast moving opener rolls, possess great momentum in the direction they were travelling at the point of release--usually downward. Secondly, to move a tuft side-ways, relative to the direction of travel, requires the application of a side-ways force and time, and time requires travel distance. Thirdly, the art usually places the distance, between the opener roll and the top of the column of stock in the batt forming chamber, at something between 16 to 24 inches (due to practical ceiling height limitations). Consequently, there is precious little time for a fast travelling tuft to do much side-ways movement. Therefore, such pneumatic prior art devices often fail to measure up to performance expectations. Due to their sheer complexity and for other reasons which will become apparent below these type systems are unsuitable to meet the objects of the present invention.
It is known in the art (for example, U.S. Pat. No. 3,787,093) that a plurality of fan wheels may be placed inside a batt former to pressurize the column of stock contained within such batt former. The fan wheels draw tufts and fibers from a distribution system and fling them downward into the batt forming region beneath the fan wheels. The prior art teaches that a guide member or members may be slidably mounted or pivotably mounted within the batt former, in order to attempt to control the air currents and/or tufts flowing around therein. Each pound of common textile fibers contains literally millions of tiny fibers--each having a diameter which is much finer than a human hair. For batt formers operating at production rates of 100 to 200 pounds per hour, over a billion fibers flows through such devices in just a short period. Whenever slidable or pivotably mounted plates are inserted within a highly pressurized batt forming device, operating clearances must always be provided between the movable plates and the machine walls. The billions of tiny fibers flowing are constantly "looking" for joints, cracks, crevices in which to become lodged. With such high numbers present, the mathematical probability that a snag point will be found is quite high. Once a single fiber becomes lodged, others aerodynamically spin on it, due to turbulence and swirls, until ropes are formed. The ropes flop around and interfere with the proper distribution of tufts and air currents within such devices. Additionally, when such tightly spun ropes do occasionally break loose, they are very detrimental to the carded quality of the product. These ropes have been known to choke down and even destroy carding machines. It is well known that centrifugal fans are inefficient devices from an energy consumption point of view. Therefore, the required use of two or more such fans within a batt former is particularly wasteful of energy. For these and other reasons which will become apparent below, this prior art has serious operating disadvantages.
It is known in the art (for examples, U.S. Pat. Nos. 3,400,518 and 3,708,210) that fiber condensing screens may be constructed by the parallel alignment of a plurality of flat bars (long side facing the tufts), or T-shaped bars, or L-shaped bars. The bars are disposed so that spacing gaps between each of the bars form a plurality of vertical slots. The slots allow the passage of air into an exhaust chamber, from a fiber condensing chamber, while restraining the tufts deposited within the fiber condensing chamber. It is also known in the art (for example, U.S. Pat. No. 3,482,883) that another type of fiber condensing screen may be constructed by placing a plurality of thin rods parallel to each other, so that air exhaust slots exist in the spacing gaps between each of the thin rods. Such prior art screens have two common characteristics. First, the thickness of the screens (or the depth of the slots) measured away from the tufts contained within the fiber condensing chamber, is quite thin. Secondly, each of the aforementioned air slots results in an abrupt "flow area" enlargement upon entering the air exhaust chamber. Anytime air passing through a slot-like orifice experiences an abrupt "flow area" enlargement, swirls, eddies and turbulence results. Since many of the tiny hair-like fibers also project through the shallow (thin) slots, while the tufts (from which the projecting fibers are attached) are restrained within the condensing chamber, the swirls in the exhaust chamber causes the projected fibers to be aerodynamically spun and twisted together to form highly detrimental neps. This is a serious operating disadvantage.
It is known in the art that a hopper feeder may be used to supply fiber to a carding machine and such art may be seen, for example, by reference to U.S. Pat. Nos. 3,070,847; 3,738,476; 3,548,461; and 3,562,866. With such art, the objective is to provide a fairly uniform cross-direction density profile in the batts they ultimately form. They attempt to accomplish this by rolling and tumbling a ball of stock contained within the hopper, by an upward moving pinned apron, while the pinned apron extracts tufts from the rolling ball which are deposited into a batt forming chute located down stream. Because the aprons of such devices are comprised of slats loaded with pins which are usually spaced apart about one inch (25 mm), the fiber separation potential of the devices is severely limited. Again, a pound of common textile fibers contains at least one million fibers. If a pound is fortunate enough to be engaged by as many as 1,000 pins (unlikely), this means that the smallest tuft produced will itself contain over 1,000 fibers. These large tufts are unsuitable for high production, high quality carding. Additionally, because of side wall friction in the batt forming chamber, hopper feeders produce batts which have a undesirable cross-directional density profile such as that illustrated in FIG. 4. For these and other reasons which will become apparent below, such art is unsuitable to meet the objects of the present invention.
When processing certain types of fibers (for example, cotton which must pass through elaborate cleaning steps before it is suitable for presentation to a carding machine), it is sometimes preferable to supply fiber to a group of cards from a central supply point. Usually a pneumatic transport system is used which deposits fiber into batt forming devices located at each of the various carding machines in a line. In order to attempt to achieve a fairly uniform cross-directional density profile in the batts delivered by the batt formers of such systems, it is known in the art to arrange the cards of a processing line in an "end-to-end" fashion and flow tufts "longitudinally" down a main transport duct, which passes over the cards in their running-direction. This art may be seen, for example, by reference to U.S. Pat. Nos. 3,029,477; 3,300,817; 3,414,330; 3,112,139; 3,326,609; 3,552,800 and Re. U.S. Pat. No. 27,967. Here the theory is that a long shallow transport duct, that is the full width of the batt formers, will cause the tufts to be distributed evenly across the widths of the various batt formers as the tufts are deposited therein. However, because of the effects of sidewall friction in the batt formers, they produce a batt having the undesirable cross-directional density profile illustrated by FIG. 4. Additionally, the "longitudinal" or "end-to-end" arrangement of carding machines is non-optimum for many yarn making applications. Carding machines are about 3 times as long as they are wide. Consequently, the "work-path" which must be travelled by a card tender or operator, doffing cans of sliver and transporting them to a subsequent process, is much longer than if the line of cards can be arranged "side-by-side". Because of these reasons and others which will become apparent below, such art is not suitable to meet the objects of the present invention.
Arranging a line of cards "side-by-side" and using a "transverse" method of supplying fiber to the various cards by flowing the large tufts from a central supply point "crosswise", with respect to the running-direction of the cards, is preferable in most yarn making applications. This art can be seen, for example, by reference to British Patent No. 1,113,033 and U.S. Pat. Nos. 3,473,848; 2,964,802; 3,474,501; 4,476,611; 4,136,911; 3,450,439; 3,667,087; 3,145,426; 3,903,570; and 3,896,523.
Because the stock is flowing first in one direction and then must abruptly change direction, this method of supplying fiber to cards is fraught with many special problems and disadvantages.
Classic examples of pneumatically supplied batt forming devices are disclosed in U.S. Pat. Nos. 4,656,694 and 4,779,310; the latter of which is directed to a control device for reducing the weight errors which are often caused by prior art batt formers. Generally, in this type device, fibrous stock, in large tuftular form, is pneumatically conveyed from a central supply point by a large powerful fan. The fan is connected to a main transport duct which may pass over a group of batt formation machines (Prior art FIGS. 10a and 10b). The combined actions of gravity and the bleeding of a portion of the main transport air out through screens, disposed along the front and rear walls of the upper fiber reserve chute causes some of the tufts to be extracted from the main transport duct and deposited into the upper reserve chute. A high positive static pressure P5 operates atop the column of fibers in the reserve chute and compresses them downward against a feed roll between the reserve chute and a batt formation chamber.
With the flow down the main transport duct (as shown) the momentum of the fast travelling, coarsely opened tufts causes them to be piled against the left sidewall of the reserve chute (Prior art FIG. 10b). This causes the cross-directional density profile of the batt "seen" by the feed roll to take on the appearance illustrated in prior art FIG. 10c. This density profile is "lighter" on each side because of the sidewall friction existing in the reserve chute, and skewed off-center due to the momentum of the deposited tufts.
The feed roll presents stock to an opener roll which plucks tufts therefrom and, primarily by centrifugal forces, doffs itself of such tufts by flinging them downward into the bottom batt formation chute. There, a high positive static pressure P6 compresses the tufts to form a batt which is fed outward and downward to a conventional carding machine. Static pressure P6 is caused by a fan, which pressurizes a plenum chamber to attempt to cause a fairly uniform velocity sheet of air to exit through an orifice slot located at the bottom of the plenum chamber. The exiting sheet of air flows generally along a guidesheet and down into the bottom chamber. At this point, the airflow is exhausted through front and rear screens and, is returned to the inlet of the fan.
In theory, any deficiency of tufts--to block off the screens in the formation chamber--will be filled by tufts deposited thereon by the sheet of guide air flowing into the bottom chamber--because the airflow should be greatest in the regions of screens having the most "open" area. This reliance on passive control means to adjust the cross-directional density profile is not totally effective. The resulting density profile of the batt leaving the formation chamber takes on the appearance illustrated by prior art FIG. 10d. That is, it is still skewed in the direction of flow of tufts in the main transport duct, but is somewhat improved symmetrically over the batt leaving the upper reserve chute. It is still "light" on the edges. The "lighter" edges result, of course, because of the sidewalls friction acting on the fibers in the bottom chamber, and the fact that the cross-directional velocity profile in the sheet of guide air is likewise adversely affected by the sidewall friction of the batt forming machine.
A static pressure, almost equal in value to P6, exists in the region between the opener roll and feed roll. This static pressure tends to resist the downward flow of the fibers in the stock column and must be counteracted by having an even higher positive static pressure P5 in the main transport duct. There is a practical upper limit as to how high static pressure P5 can be raised, because the increased potential energy level can cause severe chokes, or fiber jams, in the main transport duct. This happens whenever any pressure imbalance exists between the batt formation machine shown and the other batt formation machines which are operating in parallel, because they are all connected to the same transport duct. Such feeding systems have a well known propensity to choke because of such pressure balance sensitivity.
Since such feeding systems are usually employed as a group of batt formation machines connected to the same transport duct, the static pressures developed by their respective individual fans tends to work against, or "fight", the main supply fan which is propelling the stock down the main transport duct. This is a serious misuse of energy, and aggravates the pressure balance sensitivity of such feeding systems because there are frequent occasions when one or more of the batt formers in a feed line must be stopped; because of either a routine "end down" (web breakage) or maintenance being performed on one of the carding machines in the line. Furthermore, since there is a practical upper limit imposed on pressure P5 there is, by consequence, corresponding upper limits imposed also on the pressures P6 operating in the various batt formers. This deprives such prior art systems from the opportunity to be able to pack the batts being formed with an optimum higher pressure. Still further, pressure P5 is constantly fluctuating up and down as the various screens of the various reserve chambers become covered or "blocked" with tufts, as stock flow is intermittently started and stopped from the central feeding point, and as the "back-pressure" from the filtration system fluctuates due to "loading" and "stripping" of the filter media. Fluctuations in P5 are immediately reflected in fluctuations in P6, which is working against it, and the results are adverse fluctuations in the densities of the batts leaving the batt formation chutes. It is primarily to compensate for these undesirable pressure fluctuations and interactions, that elaborate control systems such as disclosed in U.S. Pat. No. 4,779,310 have been proposed.
Classic opener rolls in such feed systems are usually constructed using between 4 to 8 pinned bars, disposed linearly across the width of the opener roll. Each pinned bar is populated with pins spaced apart approximately 1 inch (25 mm) along their length. Assuming the maximum of 8 pin bars is used, and a typical opening roll diameter of 10 inches, and a nominal 38 inches working width opening roll, this computes to a maximum "point density" of about 0.2546 points per square inch of working surface on the opening roll. Since the primary doffing mechanism consists of centrifugal forces flinging off the tufts, a higher pin density over the surface of opener roll does not work properly because the size of the tufts becomes so small that the centrifugal forces become less operative. Likewise, the angle of attack of the pins on the pinned bars cannot be too aggressive toward the fibers because of the difficulty in doffing the tufts from the pins. It is noteworthy that in prior art FIG. 10a, the sheet of air flowing along the guide plate is placed at a significant distance off the tips of the pins of the opening roll. These factors all limit the degree of fiber-to-fiber separation possible with the prior art.
Thus, the classic prior art suffers from the adverse effects of sidewall friction, the reduced potential for fiber-to-fiber separation, the adverse effects of pressure sensitivity on the reliable operation of the stock distribution system, and a serious static pressure limitation imposed on the value (non-optimum) which may used in the bottom batt formation chamber to compress the tufts therein.
Accordingly, an object of the invention is to provide a textile apparatus and method for increasing the fiber openness and separation during the processing of textile fibers.
Another object of the invention is to provide a textile apparatus and method wherein the cross-direction density profile of fibers across a batt or sheet of fibers is accurately controlled.
Another object of the invention is to provide a textile apparatus and method which provide total flexibility as to the plying of fibers to associated textile machinery and processes.
Another object of the invention is to provide a simple and efficient textile feeding module which may be universally adapted to accept fibers from any type of source of supply.
Another object of the present invention is to provide a batt forming apparatus which is suitable for receiving fibers from either a hopper feeder (permitting individual card-to-card supply flexibility), or alternatively being connected, as one of a group of batt formers, to a common feeding point (so that all may be supplied from the same source), and which may be easily and quickly switched from one supply mode to the other, so that the textile industry can more readily exploit the profit opportunities offered by the "just-in-time" and "quick response" manufacturing concepts.
Another object of the present invention is to provide a batt forming apparatus which may utilize a very high static pressure in its batt forming compaction operation but which does not interfere with the flow of stock into the batt forming apparatus, irrespective of the mode of supply.
Still another object of the present invention is to provide a textile apparatus and method by which fibrous tufts may be highly opened, or separated to an almost fiber-to-fiber state, by an opening roll, which may contain on its surface a very large number of teeth per unit area and such teeth may be positioned to present a high angle of attack toward the fibers.
Another object is to provide an efficient means to doff the fibers impaled on the teeth of such an opening roll.
Yet another object of the invention is to provide a fluidized mixture, of highly opened fiber bundles and transport air which causes the fiber to be deposited into a batt forming chamber in such a way that, after being acted upon by a high positive static pressure, a batt having a very high running-direction evenness and a desired cross-directional density profile results.
Another object of the invention is to provide a means of separating the conveying air from the highly opened fibers in such a way that a portion of such air may be advantageously used to efficiently doff an opening roll.
Another object of the invention is to provide an improved carding machine which may be operated at very high production rates without the need for additional licker-in cylinders which have heretofore been necessary in order to achieve a comparable high rate of production.
Another object of the present invention is to provide a means to custom tailor the cross-directional density profile of the batt fed into a carding machine such that the web delivered by the carding machine need not suffer from lighter selvages than the weight of the web near the center of the carding machine so that it can operate at higher speeds without adverse windage effects, and the need for the addition of complex web shielding or collection devices.
Another object of the present invention is to provide an improved carding machine which is universally suited for making either a non-woven web or a sliver, because such card includes a device which custom tailors, in a desired manner, the weight per unit area of the web leaving the carding machine and obviates the need for web gathering devices.
Another object of the present invention is to provide a batt forming apparatus which obviates the need for either complicated external screen damper plates or problematical internal steering plates which have heretofore been necessary in order to vary the cross-directional batt density profile.
Another object of the invention is to provide a means of separating the conveying air from the highly opened fibers in such a way that a portion of such air may be advantageously directed to supercharge the boundary regions near the sidewalls of the batt forming apparatus, so that the velocity profile of the doffing air knife may be optimized and thereby it requires a minimum amount of operating energy.